Method of making papermaker{3 s felt

ABSTRACT

A papermaking felt has an essentially three-layer construction including a cushion of non-woven batting material interposed between a relatively fine woven finish fabric and a preferably coarser woven wear fabric, and these respective portions of the felt are anchored together by one or more needling operations. The finish fabric is fine enough weave to prevent undesirable marking of a sheet of paper, and the wear fabric is strong enough in construction to resist the abrasion and wear and open enough to permit water to pass freely through the felt. The intermediate batt is thick enough to resist compression occasioned by the high pressures of normal paper machine speeds and joins the finish and wear fabrics in unitary construction to prevent the fabrics from shifting relative to each other during operation.

United States Patent [1 1 Ivanowicz [451 Nov. 20, 1973 METHOD OF MAKING PAPERMAKERS FELT Related US. Application Data [62] Division of Ser. No. 1,241, Jan. 7, 1970, Pat. No.

FOREIGN PATENTS OR APPLICATIONS 113,116 4/1941 Australia 28/4 R Primary Examiner-Louis K. Rimrodt Attorney-Lawrence B. Biebel et al.

[5 7 ABSTRACT A papermaking felt has an essentially three-layer congti n q ydin a cushion Qfnsmrwwn P es material interposed between a relatively fine woven finish fabric and a preferably coarser woven wear fabric, and these respective portions of the felt are anchored together by one or more needling operations. The finish fabric is fine enough weave to prevent undesirable marking of a sheet of paper, and the wear fabric is strong enough in construction to resist the abrasion and wear and open enough to permit water to pass freely through the felt. The intermediate batt is thick enough to resist compression occasioned by the high pressures of normal paper machine speeds and joins the finish and wear fabrics in unitary construction to prevent the fabrics from shifting relative to each other during operation.

3 Claims, 4 Drawing Figures PATENTEB MW 20 I975 PRESSURE FIG - v d I W METHOD OF MAKING PAPERMAKERS FELT This application is a division of Ser. No. 1,241, filed Jan. 7, 1970, now U.S. Pat. No. 3,657,068, granted Apr. 18. 1972.

' BACKGROUND OF THE INVENTION The present invention relates to needled papermaking felts and to methods of making them. Such felts are commonly used for supporting and draining paper making material during the papermaking process.

In recent years the speeds of papermaking operations have increased to the point that greater roll pressures have been necessitated which cause an increase in the tendency of felts to mark the sheets of paper as they pass through the nip and to wear excessively as they pass over the machine rolls, suction boxes, and cleaning equipment. The problems presented resulting from the increased production requirements vary depending upon the conditions under which the papermaking operation takes place (temperature, humidity, etc.), the number of abrasive surfaces over which the felt travels, the condition of the papermaking machinery and various other factors known to persons skilled in the felt making art.

The ideal papermaking felt should have at least the following properties. First, it should have a surface that is fine enough to produce a smooth finish and minimize marking of the sheet of paper being produced. Second, it should be open enough to allow water to drain through it without significant impedence. Third, it should be resilient enough to quickly recover from repeated high nip pressures over a long period of time. Fourth, it should be tough and strong enough to provide good stability, wear resistance and felt life.

Batt-on-base needled felts which consist of a batt or fleece of loosely associated non-woven fibers needled to a woven base fabric are well known to the art and possess several of the characteristics of the ideal felt such as a smooth surface, and openness. Because of their relatively high drainage characteristics these felts have been extensively used throughout the papermaking industry.

However, several problems have been encountered with the batt-on-base needled felts. One problem is that the abrasive action of the press rolls causes the batt surface which receives the paper to shed fibers after a relatively short period of use. Such fibers cause printing problems and mark the paper, resulting in an inferior finished product. Another problem has been that the nip pressures pack down the batt to the point that the fibers are so closely spaced that the felts drainage characteristics are severely impaired. When the felts bulk and cushion properties are substantially reduced, the paper web is marked more readily. It has also been found that with these felts some of the water remaining within the batt fibers after water is expelled from the paper at the nip tends to seep back into the paper by capillary action to rewet the paper. When the batt is packed down the tendency for rewetting to occur is increased.

Another problem is that it has proven difficult to produce a needled felt which will withstand the excessive abrasion and wear caused by the pull of the papermaking machines under high roll pressures and speeds. The base fabric in such felts have of necessity been of a relatively fine construction so that the individual fibers could be adequately anchored to prevent shedding as much as possible, but fine base fabrics have relatively low stability and resistance to wear and abrasion and consequently such felts are plagued by distortion and have shorter service lives than is desirable.

SUMMARY OF THE INVENTION The present invention is directed to an improved felt which has increased bulk and cushion properties and increased wear resistance, and to a method of making the same. The invention substantially increases felt service life by reducing shedding and increasing strength to meet the increased production speeds and pressures now common in the industry. Generally, the felt has an essentially three-layer construction comprising an intermediate batt or fleece of non-woven material which is sufficiently thick to provide increased bulk and resiliency for offsetting the higher nip pressures and which is bounded on one side by a relatively fine fabric for providing finishing quality and on the other side by a preferably coarser fabric for providing stability and wear resistance. The internal batt is anchored to these fabrics preferably by a needling process to form a strong integral felt.

In accordance with a preferred embodiment of the present invention, the fine fabric is of a S-harness satinweave construction to provide a smooth surface which is relatively free of knuckles and cross-over marks in order that a high degree of finish may be obtained for the paper sheet. The coarse fabric is preferably of a plain-weave construction to provide for ease of drainage, and preferably has a high-synthetic content for added strength and wear resistance.

The felt is preferably made in the following manner. The fine fabric is woven and fulled as desired. It is then installed on a needle loom and non-woven batting material, which may be all wool, or a blend of synthetic and wool, or all synthetic, is applied to the back side thereof. The batting is of sufficient weight to give good bulk and cushion properties. The batting is then intimately anchored to the fine fabric by one or more needling operations. Next, a coarser fabric is inserted on the needle loom above the needled batting material and this fabric is needled into and through both the intermediate batting and the fine fabric.

The resulting felt has a smooth finish surface which effectively contains strike-through and shedding of the intermediate cushion material. The'construction of the wear fabric permits any water passing through the finish fabric and the cushion to drain from the felt with a minimum of impedence, while the intermediate cushion material not only adds resilience but also prevents the fabrics from shifting relative to each other. The fine finish fabric cooperates with the coarse wear fabric to help prevent water in the batting after it has passed the nip from seeping back into the web.

DETAILED DESCRIPTION OF THE DRAWING FIG. 1 is a perspective and somewhat diagrammatic .view showing the needling of a batt or fleece of non- I woven batting material into the back of a fine finishing dling and showing the felt in its upright web supporting position; and

FIG. 4 is a diagram of a paper machine press.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a fine fabric which preferably has been finished to size is shown diagrammatically as being positioned on the horizontal surface ofa needling machine. It preferably has a relatively fine five-harness satin-weave construction (FIG. 3), wherein the yarns are single in both the warp and filling directions, but may be of a construction corresponding to any of the felt classifications ranging from Pulp, Common Wet, Fine Wet, Superfine Wet, Extra Superfine Wet, Fine Press, Super Press, Plate Press, Super Plate Press, and Yankee Pic-up. The fabric 10 may therefore be varied in design, yarns, weave, weight and end and pick count, as desired. The finish fabric 10 may be fulled or nonfulled and may be woven endless, but in practice it is preferred that it be formed as one length to be eventually spliced together to form an endless felt.

As shown in FIG. 1', a batt or fleece of non-woven batting material 12 which has preferably been finished to size is applied to the back 14 of the finish fabric 10. The batt of fibers 12 is preferably comparatively thick and has a weight on the order of one-half ounce per square foot, but the amount and weight thereof may be varied to suit different operating conditions and purposes. This batt material 12 is preferably a relatively fine grade of wool but a substantial portion or all of it may consist of synthetic material for purposes of increased bonding strength.

In practice, the batting material 12 may be needled into the finishing fabric 10 by two passes under the needling head 16 at 9/16 inch penetration and H12 inch advancement per stroke. The barbs 17 of needling head 16 are preferably oriented in the filling direction and are purposely fixed at incremental displacements which will penetrate the filling yarns l8 and minimize penetration ofthe warp yarns 20 (FIG. 3) so that these latter yarns which carry the load will not be substantially weakened. This is shown in the drawing by the greater number of fibers penetrating the filling yarns 18 as opposed to those penetrating the warp yarns 20.

The needling process compacts the batting material 12 against the back 14 of the fabric 10 so that it is intimately interlocked therewith and fills into the spacings, for example at point 22 (FIG. 3), between the hills 24 and the valleys 26 formed by the warp and filling yarns. In such a needling operation comparatively few of the fleecy fibers pass through the fabric.

After the batting has been needled to the finish fabric a second preferably coarser fabric 28 (FIG. 2) which has preferably been finished to size is threaded around the needled batt 12 already on the loom. Fabric 28, like fabric 10, may have a construction corresponding to any of the felt classifications depending upon the operating conditions and purposes. It may be all wool, or all synthetic, or a blend of wool and synthetic yarns, but is preferably comprised substantially or totally of tough and strong, highly synthetic yarns in both the warp and filling directions and may have a plain weave construction. The plain weave and the low end and pick count of this type of material will facilitate subsequent splicing when the three needled components are joined to form an endless felt.

The needling head 16 is brought into position (FIG. 2) and the wear fabric 28 is needled into and through both the intermediate batting cushion 12 and the finish fabric 10. This may be accomplished, for example, by using a inch penetration and a 27/64 inch advancement per stroke. Initially, only one round of needling is necessary. As before, the barbs 17 of the needling head 16 are preferably controlled to contact the filling yarns 30 and to minimize penetration of the warp yarns 32, and the needling process forces the wear fabric 28 into the batting 12 so that the batting fibers fill into the spacings, for example spacing 34, between the hills 36 and valleys 38 formed by the warp and filling yarns.

The felt of the present invention may as well be needled together by needling the batt material to the base fabric and then needling the fine fabric to the batt and base fabric. However, the method described above is preferred because after the barbs have passed into or through the finish fabric and are retracted they will pull some batt fibers back into the finish fabric. This method leaves fewer batt fibers on the surface of the finish fabric and minimizes scarring or tearing of the finish fabric.

The fabrics 10 and 28 are not intended to be limited only to woven fabrics, but also may be non-woven fabrics, such as those made with dissolvable filler yarns in accordance with U.S. Pat. Nos. 3,40 l ,467 and 3,458,911, issued to the same assignee herein. Such fabrics would, however, require that the barbs be oriented to anchor batting material to the warp yarns, and therefore woven fabrics with filler yarns are preferred.

The open ends of the resulting felt are spliced together and the entire fabric needled again at, for example, inch penetration and 9/64 inch advancement per stroke to provide a second needling operation for forming an endless felt with thickness-interlocked fibers. The filling of the batting material into the respective valleys of the differently sized fabrics lends resilience to the felt. When combined with the strong fabric-tofabric bonds formed by the needling operations, this filling also helps to prevent the fabrics from shifting relative to each other under the influence of high roll pressures (FIG. 4). Any strike-through which occurs is easily singed off and vacuumed away to produce a felt having a smooth, hair-free surface on the finishing side thereof and a tough surface on the driving side thereof.

A felt made according to the present invention was subjected to tension tests from 2,000 pounds to 10,000 pounds pressure, at 1,000 pound intervals, and showed no evidence of fabric separation or distortion. All three components were uniformly linked together to form a tough and strong integral felt. Shedding of batting material was essentially eliminated by reason of the presence of the finish fabric and the added anchoring of the batting material to two fabrics instead of one.

The felt of the present invention preferably has a substantial increase in thickness from an average thickness of 0.2142 inch for the conventional batt-on-base needled felts to 0.2645 inch, or on the order of about 23 percent increase. The somewhat thicker intermediate batting material acts as an absorber. Thus, the felt springs back or recovers more readily from high nip pressures of the rolls of a press section as shown in FIG. 4, and this resiliency is retained for a longer period of time than is possible with conventional felts.

In the preferred embodiment of the present invention, the felt is normally heavier and thicker than conventional batt-on-base felts so that it can withstand distortion and deformation at high pressures. It has increased strength in both the warp and filling directions, and the finishing fabric withstands abrasion substantially more effectively than a batting finishing surface. Having a fabric for the finish surface keeps the felt open and helps to withstand the tendency of the batting material to compress. The coarse wear fabric resists wear and abrasion more effectively than the relatively light weight base fabrics used on conventional felts. Also, the combined'fine construction of the finish fabric and coarse construction of the wear fabric causes the water in the batting material to move away from the web and drain through the wear fabric.

Accordingly, the felt of the present invention maximizes each of the four characteristics an ideal felt should have: finish, bulk and cushion, drainage, and wear resistance. It should be appreciated that the details of the needling process may be varied to achieve felts of different qualitative properties, such as by changing penetration, type of batting, batt mass, type of needle, needle penetration, fabric advancement, etc. without deviating from the concept of the present invention. Further, by varying the type of weave (plain, broken twill, 4-, 5-, or 6-harness satin, etc.), the warp and filling yarns (weight, size, twist and ply) and the pick count of the respective fabrics, and by varying the thickness and type of batting materials, the openness and permeability of the felt may be changed to suit different web classifications. The respective fabrics may also be made wholly of synthetic materials, or contain a substantial portion of synthetic materials, and may be chemically treated or left untreated when shipped, as desired.

While the products and method herein described constitute preferred-embodiments ofthe invention, it is to be understood, that the invention is not limited to these precise products and method, and that changes may be made therein without departing from the scope of the invention.

What is claimed is:

1. A method of manufacturing an essentially threelayered papermakers felt having a fine finish fabric, an intermediate cushion batting, and base fabric on a needle loom comprising the steps of installing the woven finish fabric having warp and filling yarns on the needle loom, applying non-woven batting to the back side of the finish felt sufficiently thick to give good bulk and cushion properties, needling the batting into the finish fabric by needle penetration through the batting and into the finish fabric with the penetration being predominantly through the finish fabrics filling yarns, installing a woven base fabric having warp and filling yarns on the needle loom over the exposed side of the needled batting, and needling the base fabric into the batting by needle penetration first through the base fabric, then through the batting and finally through the finish fabric with the needle penetration being predominantly through the base fabrics filling yarns.

2. The method of claim 1 further including the step of finishing said fabrics to size prior to installing on said loom.

3. The method of making a papermakers felt comprising the steps of placing a relatively light-weight finish fabric on a needling loom, applying a non-woven batting to the inside surface of said finish fabric by needle penetration first through the batting and then through the finish fabric with sufficient needling to anchor the batting to the finish fabric, applying a relatively coarse woven base fabric to the exposed surface of the batting, and attaching the base fabric by needling with the needles penetrating first through the base fabric, the batting, then the finish fabric so that retraction of the needles has the effect of pulling batting fibers back to the finish fabric. 

1. A method of manufacturing an essentially three-layered papermaker''s felt having a fine finish fabric, an intermediate cushion batting, and base fabric on a needle loom comprising the steps of installing the woven finish fabric having warp and filling yarns on the needle loom, applying non-woven batting to the back side of the finish felt sufficiently thick to give good bulk and cushion properties, needling the batting into the finish fabric by needle penetration through the batting and into the finish fabric with the penetration being predominantly through the finish fabric''s filling yarns, installing a woven base fabric having warp and filling yarns on the needle loom over the exposed side of the needled batting, and needling the base fabric into the batting by needle penetration first through the base fabric, then through the batting and finally through the finish fabric with the needle penetration being predominantly through the base fabric''s filling yarns.
 2. The method of claim 1 further including the step of finishing said fabrics to size prior to installing on said loom.
 3. The method of making a papermakers felt comprising the steps of placing a relatively light-weight finish fabric on a needling loom, applying a non-woven batting to the inside surface of said finish fabric by needle penetration first through the batting and then through the finish fabric with sufficient needling to anchor the batting to the finish fabric, applying a relatively coarse woven base fabric to the exposed surface of the batting, and attaching the base fabric by needling with the needles penetrating first through the base fabric, the batting, then the finish fabric so that retraction of the needles has the effect of pulling batting fibers back to the finish fabric. 